Method and apparatus for welding



. 17, 1939. J. v. CAPUTO METHOD 'AND APPARATUS FOR WELDING OriginalFiled March 14, 1934 4 Sheets-Sheet 1 I Nw lr'lven tor Zjames V. Ca puto Oct. 17, 1939. J. v. CAPUTO 2,176,656

METHOD AND APPARATUS FOR WELDING Original Filed March 14, 1934 4Sheets-Sheet 2 l /rlventor lgj gi vCaputo \Q m, MIM

Oct. 17,. 1939.

J. v. CAPUTO 2,176,656

METHOD AND APPARATUS FOR WELDING Original Filed March 14, 1934 4Sheets-Sheet 3 lnven tor James llC'apu'to 1939. J. v. cAPuTo 2,176,656

METHOD AND APPARATUS FOR WELDING Original Filed March 14, 1934 4Sheets-Shet 4 III III I ll lnven to! dames V. Capu to Patented on. 17,1939 James 4V. Caputo, Grafton, Pa. Original application March 12 1934,Serial No.

Divided and this application January 16, 1937, SerialNo. 120,941

21 Claims. ((11. 1'71-9'1) My invention relates to the art or electricwelding and, in particular, to the continuous welding of seams betweenabutting plate edges.

It is described herein as applied to the welding 5 of axial seam cleftsin formedtube blanks, although it is not limited thereto.

The invention described and claimed herein isdivided from my Patent No.2,09il,952, dated November 16, 1937, for Method and apparatus forwelding.

It is recognized in the electric welding art that direct current ishighly desirable for welding because of the uniformity and continuity ofthe Weld produced thereby. Considerable difllculty has been experienced,however, in the generation, transmission and control'of direct currentsof the magnitude necessary to weld plate edges of substantial thicknessat a high rate, for example, currents of the order of hundreds of 2cthousands of amperes. Ordinary commutator types of direct-currentgenerators are, of course, not well suited to the generation of suchlarge currents. The transmission problems are com plicated by thenecessity for using massive conga cluctors and the fact that a number ofparallel circuits of difierent resistance may exist, giving rise tocirculating currents or non-uniform distribution of current in theconductors resulting in excessive heating and losses. The latterseriously so affect the generator and may even preclude thesatisfactoryoperation thereof.

The control, of large direct currents has also been found diiiicultespecially in-the matter of initiating and terminating the flow of suchheavy currents as are necessary in welding. The inductance of a circuitadapted for carrying large currents is necessarily considerable, whileits resistance must be small unless excessive losses.

are to be incurred. These conditions, therefore, 40 have necessitatedconsiderable intervals of time for building up and terminating thewelding current and have resulted in imperfect welds where the seamimpedancevaries for any reason. In continuous welding of tubes, forexample, the practice success of any particular method or apparatus maybe gauged rather well by the amount of end scrap loss, of which -asubstantial portion is the length whichitis necessary to crop from eachendof the welded article to remove the incompletely welded portion. Itis necessary, furthermore, in contact resistance welding that the workbe in engagement with the contact electrode before the welding currentbegins to flow, to prevent arcing and burning of as the electrodes. Fort sa e r a the current must be terminated before the work leaves theelectrode. In order to operate at high speeds,

therefore, the welding current must be built up with exceeding rapidityand terminated in a similarly short interval of tlmewhen the welding ghas been completed.

It will be obvious from the foregoing that the requirements of asuccessful direct-current welder are more or less inconsistent and ithas been difficult, impractical, or impossible, to pro- 10 videequipment which would satisfactorily meet all the necessaryrequirements.

I have invented a method and apparatus for welding including adirect-current generator and.

a control and current supply system cooperating w therewith, to applydirect current to continuous contact resistance welding of plate edgesof sub stantial thickness at high speeds. The invention provides asatisfactory solution to the problem of. generating, transmitting andcontrolling direct 2g currentsof large magnitudes for the purpose ofcontinuous electric 'welding. The arrangement of the circuit between thegenerator and the welder is such that circulating currents arepracticularly eliminated and a substantially uniform g distribution ofcurrent in the various portions of the circuit is obtained. This reducesthe heating and losses occurring in the transmission circuit and alsomakes practical the operation of the generator.

Otherfeatures of novelty will become apparent with the progress of thefollowing description, which is to be read in connection with theaccompanying drawings illustrating a present preferred embodiment of theinvention together with 35 certain modifications thereof. In thedrawings:

Figure 1 is a plan view, largely schematic, of, the apparatusconstituting the welding system of my invention; 7

' Figure 2 is a side elevation corresponding to 40 Figure 1;

Figure 3 is a side elevation of a series or compound exciter forfurnishing excitation to the main welding generator;

Figure 4 is an end view corresponding to 45 Figure 3; Figure 5 is apartial side elevationwlthparts in section, of a slip ring assemblydisposed between the generator and the welder for conducting currentfrom the fixed generator leads to the rotatso ing welding electrode;

' Figure 6 is a partial plan view of the slip ring assembly, with partsbroken away for clearness;

Figure 7 is a sectional view taken along a radial o5 plane through the.axis of the assembly of Figure 5;

Figure 8 is a sectional VIII-VIII of Figure 7;

Figure 9 is a schematic diagram of connection of the welding circuitincluding the internal connection of the welding generator and slip ringassembly.

Referring now in detail to the drawings and, for the moment, to Figures1 and 2, the invention includes an electric welder I0 having a basecolumns l2 and a head l3, A carriage I4 is slidably supported on thecolumns 2 by a fluid suspension l5 and springs IS. The suspension l5permits lifting the carriage above the limit of movement due to thesprings. Screwdowns IT for adjusting the carriage are driven by a motorl8.

Pressure rolls |9 are adjustably mounted in a base 20, which is itselfcapable of adjustment on the base A welding'electrode 2| is supported inbearings mounted on the carriage l4. The electrode is composed ofinsulated conducting discs adapted to engage the edges of an axial seamcleft in a formed tube blank shown at 22. The construction of the welderl0 and electrode 2| is more fully explained and claimed in my Patent No.2,006,912.

a A plurality of conductors extend axially from the electrode 2| throughone of its,supporting bearings 23. Alternate conductors engage oppositediscs of ;the electrode and are insulated from the other disc.

Welding current is supplied to the electrode 2| through theaforementioned conductors from a generator 24. This generator ispreferably of the homopolar type, as described and claimed in my PatentNo. 2,005,609. The generator terminals are shown at 25 and 26 and eachcomprises a plurality of conducting bars of opposite polarity ininterleaved relation. As shown in Figure 1, the individual conductors ofthe terminals 25 and 26 are interleaved and are fanned out a shortdistance from the generator. This permits the dimensions of the slipring assembly to be kept to a minimum. By reason of the interleaving,adjacent bars are of opposite polarity, the conductors of one polaritybeing sandwiched in between those of the other polarity. Flexibleconnectors 21 join the bars of the terminals 25 and 26 to a plurality ofbars 28 having a loop 29 formed therein. The loop 29 links the core 30of a series compound exciter 3| driven by a motor 32, which will beexplained more fully later.

Flexible connections 33 similar to those shown at 2! join the bars 28 tosimilar bars 34 entering a device 35, which I designate as a slip ringassembly, since it receives current from the stationary conducting bars34 and delivers it to a rotating system including the electrode 2|. Thebars forming the terminals 25 and 26; and the bars 28 and 34 are firmlyheld together in proper relative position by clamps 36 having bolts 3!extending therebetween. I

The slip ring assembly 35, which will be described in greater detailpresently, delivers current to rotating conductors 38 rotatablysupported in bearings 39. The conductors 36 and the slip rings of theassembly 35 are carried on a shaft 40. The shaft 40 is driven bya motor40m through gearing 407'. A shaft 4| on which the electrode 2| and itssupply conductors are supported, is coupled to the shaft 40 throughuniview alon the lines versal joints 42 and a connecting shaft 43. .The

joints 42 permit the welder axis to be disposed oncenter with regard tothe slip ring assembly axis, if desired. Connectors 44 extend betweenradial projections 45 on the conductors 38 and on those extending fromthe electrode 2|.

Referring now to Figures 3 and 4, the exciter 3|, in addition to thewindings 29 and core 30, comprises a frame 46, bearings 41 and anarmature 46 rotatably supported thereon between pole .example, extendaround the horizontal portion of the core 30 in one direction, while theadjacent bars 29b connected to the other terminal 26, extend across thetop of the core and around it in the opposite direction. In this way,both sides of the main circuit, that is, the conductor bars 29 ofopposite polarity, are given substantially the same length andimpedance, and a single-turn winding is provided for the core 30. Thedriving motor 32 requires no description since it may be of any desired,adjustable-speed type, effective to drive the exciter armature 48 at asubstantially constant speed when once adjusted. With the bars 291:. and29b disposed as described, the resulting magnetomotive force is in onedirection only and the flux induced in the core 30 depends on thecurrent traversing the bars. It will be apparent that by disposingcertain bars of opposite polarity in the same direction about the core,their magnetomotive forces will be differential and they will contributenothing to the excitation oi the core. In this way, the desiredexcitation of the core for full welding current may be obtairied.Further adjustment, of course, can b: made by moving the saturationbridge 50, the position, area, and saturation of which determines theproportion of the core flux which is bypassed around the pole pieces 49.The exciter 3| is obviously a two-pole machine and its output iscollected from a commutator 5| by brushes 52 in the usual manner.

Referring now to Figures 5 through 3, the slip ring assembly 35comprises an annular yoke 53 having end bells 54 and 55 attachedthereto. The yoke 53 is supported on feet 53a but may be rotated thereonto position the slip ring assembly at any desired angle relative to theshaft of the generator 24. The shaft 46 extends through the end bellscoaxially of the yoke 53 and is provided with a spider 56. A pluralityof slip rings 51 are carried on the spider 56 but insulated therefromand separated by spacers 58.

Brush holder brackets 59 and 66 disposed back to back, are secured tobut insulated from rings 6| carried by the end bells 54 and 55. Thebrackets 59 and 66 are separated by a thin layer of insulating materialsince they are connected to bars 34 of opposite polarity throughconnections which will soon be described. All the brackets 59 are of thesame polarity and likewise all the brackets 60 and, therefore, thebracket 59 of one pair is of a polarity opposite that of the bracket 60which it faces in the adjacent pair. Brush holders 62 and 63, havingbrushes 64 carried thereby, are secured to the brackets 59' and 60,respectively, of adjacent pairs. The brushes 64 on the holder 62 projectbetween the brushes on the holder 63 and engage alternate slip ringscameos 57 of opposite polarity. The engaging faces of the holders andbrackets are serrated. The connecting bolts are not shown.

Risers 68a and t lb are connected to one of the brackets 59. The upperends of'these risers are attached to theoutturned ends 65 of annularconducting bars 86, all the annular bars being interleaved and insulatedso that adjacent bars are of opposite polarity. The outcoming leads fromthe generator are arranged similarly to the annular bars 66, as shownand claimed in my Patent No. 2,005,609 and, in order to provide equalimpedance in all the parallel paths between the generator and thewelder, I connect the short leads 66 to the long leads in the generator,and vice versa, as shown diagrammatically in- Figure 9. It will beapparent that the .lengths of the difierent leads t6 vary depending onwhere they are connected to the brush holder brackets. Risers tilla and81b similarly extend from the brackets 60 to the outturned ends of theannular bars t8.

The annular bars 66, as shown in Figure 6, are contlnuations of the bars34, aresupported in the yoke tilt, and are insulated therefrom and fromeach other. The brackets 59 and 60 are insulated from the ring iii andthe bolts extending through the pairs of brackets and the risersconnected thereto are insulated from both these ele- 311811135. There iselectrical engagement, of course. between each bracket and the risersextending therefrom.

Each of the slip rings T has a row of peripheral holes alternately ofdifferent diameter, and adjacent rings are disposed so that theirperipheral holes of different diameters'are in alinement. In Figure l,the'left-hand ring has a plurality of large holes 68 therein. The nextslip ring also has, a plurality of large holes but between them, aserles'ofsmaller holes 69, the holes 69 of the second ring being in.liiie with the holes 68 of the first ring. Bars Ill extend through thealined holes and slip rings and have enlarged portions ll fittingtightly in the smaller holes and reduced portions ll-which pass throughthe large holes 68 with clearance. Insulating bushings are also disposedin the holes 68.

threaded on intermediate portions of the bars 10 Clamping nuts 13provide a good'electrical connection between the bars and the alternaterings which they engage. It will be apparent that each bar l0 engagesonly alternate rings and that the next successive bar engages the otherrings.

Flexible connections 14 extend from terminal blocks it on the bars ,lflto the insulated conducting segments 3-8 extending axially of the shaft40. A split ring 76 embraces the bars 38 and is insulated therefrom. Thering 16 is rotatably supported in one of the bearings 39. A'similar ring16 cooperates with the other bearing.

The radial projections l5 are similar to the.

connections 14 but hre not flexible. The flexibility required betweenthe shaft 40 and the shaft 43 is provided by the connectors '44. Theconductors extending axially from the electrode 2| are similar to thebars 38 and pass through the left-hand electrode bearing in the mannerdescribed in connection with the bearings 39..

It will be apparent that my invention is characterized by numerousadvantages. In the first place, I have provided a simple apparatus forgenerating and transmitting direct current of the magnitude necessaryfor welding, character-. ized by ready accessibility to all parts forinspection or renewal. The various parallel circuits between thegenerator and the welder have substantially the same impedance, so thereare no excessive circulating currents and the distribution of current ineach conductor is substantially uniform. The entire slip ring assemblymay be rotated on its supporting feet and can'thus be accommodated toany particular location of the generator leads relative thereto andregardless of any difference in elevation between the generator andwelder. The flexible connections be- "tween the welder and the currentsupply means permit considerable: latitude in the location of bothelements.

The series'exciter provides compound characteristics for the maingenerator in a very simple manner and the degree of compounding may bereadily adjusted to suit the various conditions by means of thesaturation bridge and the disposition of the conductors of the excitingwinding. The exciter driving motor, being adjustable for various speeds;provides further flexibility of control for the main generatorexcitation. The building up of the welding current and thedeterminatlon'thereof .may 'thus be accomplished with great rapidity.The interleaving of the main conductors decreases the inductance of thecircult and further reduces the time characteristic thereof.

While I have illustrated and described herein ductors extendingdifierent distances circumferentially of the generator and assembly, theleads extending the farthest distance about one of said units beingconnected to.the leads extending the shortest distance about the other,to equalize the impedance of the several connections.

2. In a supply system for a heavy-current load, a generator, and a slipring assembly between it and said load including an annular support,brushes carried thereby, a shaft extending axially of said support,rings on said shaft engaging said brushes, and interconnecting meansextending axially through said rings, having electric conductingengagement with alternate rings.

3. In a'supply' system for a heavy-current load, a generator forsupplying current thereto and a slip ring assembly between the generatorand load, comprising an'annularv supporting structure, conductorsextending circumferentially 'therein, brush-holder brackets carried onsaid structure in pairs, oppositely disposed and insulated from eachother, and means connecting said brackets respectively to certain ofsaid conductors of opposite polarity.

4. The combination with a generator, a load.

and conductors extending therebetween, of a I slip ring and brushassembly therebetween to which-said conductors'are connected, adjacentrings .of said assembly; being connected to conductors of oppositepolarities.

5. In a current supply system for a heavycurrent load, the combinationwith conductors extending from the-load spaced about a common axis, agenerator for supplying current to said conductors, a slip ring assemblybetween the generator and said conductors, an exciter for saidgenerator, said exciter having a core and being disposed between thegenerator and assembly, and conductors extending from the generator tothe assembly, said conductors being in inductive relation with the coreof said exciter.

6. The combination with a heavy-current load and a generator forsupplying current thereto, of a slip ring assembly having relativelyfixed brushes connected to the generator and conducting rings connectedto the load, said assembly including an annular structure surroundingsaid rings and supporting said brushes, and means supporting saidstructure for rotary adjustment.

7. In a current supply system, a load, a heavycurrent generator adjacentthereto having supply leads of opposite polarity extending therefromtoward the load, and an exciter for the generator disposed between thegenerator and load, said exciter having a core, and said leads ofopposite polarity being disposed in inductive relation to said core toproduce magnetization of the core in the same direction.

8. The combination with a heavy-current load and a supply generatoradjacent thereto, of as slip ring assembly for transmitting current fromthe generator to the load, said assembly comprising a support, brushescarried thereby, slip rings rotatable within said support and havingsliding engagement with said brushes, conductors connected to saidbrushes, said conductors extending circumferentially of said support andthen in an axial direction therefrom adjacent a common point to saidgenerator, and other conductors extending axially from said rings tosaid load.

9. The combination with a current-consuming device and means mounting itfor rotation, of a fixed heavy current generator adjacent the load,interleaved conductors extending from said generator to said load, and adynamo-electric machine having its field structure adjacent saidconductors forcontrolling the excitation of the igenarator to vary thecurrent supplied to the 10. The combination with a current-consumingdevice and means mounting it for rotation, of a fixed heavy. currentgenerator adjacent the load, interleaved conductors extending from saidgenerator to said load, and an exciter for said generator having amagnetic circuit in inductive relation with said conductors so as to beexcited thereby.

11. The combination with a current-consuming device and means mountingit for rotation, of a fixed heavy current generator adjacent the load,interleaved conductors extending from said generator to said load, andan exciter for said generator having a magnetic circuit in inductiverelation to said conductors so as to be excited thereby, conductors ofopposite polarity being associated with said circuit in opposite senses.

12. The combination with a generator and a load supplied thereby, of aseries exciter for said generator including a field structure and anarmature, and adjustable means for bypassing around said armature aportion of the flux traversing said structure whereby to control theexcitation of said exciter.

13. The combination with a generator, a load, and conductors extendingtherebetween, of a slip ring and brush assembly therebetween to whichsaid conductors are connected, the conductors connected to said brushesbeing curved and exconductors of tending circumferentially about saidassembly substantially to a common point, and conductors of oppositepolarities being interleaved.

14. In a current supply system for a heavycurrent load, the combinationwith a plurality of conductors extending from the load in spacedrelation circumferentially of a common axis, and a generator adjacentthe load, of leads extendin from the generator in closely groupedrelation, a slip ring assembly between the generator and load, the loadconductors having electrical engagement with the rings of said assembland connections from the generator leads extending circumferentially ofthe rings to brushes engaging said rings.

15. The combination with a current-consuming device, means mounting saiddevice for rotation, a heavy-current generator adjacent said device forsupplying curent thereto, a slip-ring and brush assembly disposedbetween said generator and said device, a group of conductors extendingfrom said assembly to terminals of both polarities on said generator,and a group of conductors of both polarities extending from saidassembly to said device, the conductors of opposite polarities of bothsaid groups being interleaved.

16. The combination with a current-consuming device, means mounting saiddevice for rotation,

a heavy-current generator adjacent said device for supplying currentthereto, a slip-ring and brush assembly on one side of and spacedlaterally from said device, a group of conductors posite polarities ofboth said groups being interleaved.

17 The combination witha current-consuming device and means mounting itfor rotation, ora fixed heavy-current generator adjacent the load,conductors extending from said generator to said load, a slip ring andbrush assembly interposed between said generator and load, theconductors extending from said generator and load being connectedto therings or brushes of said assembly, a shaft mounting said rings and meansfor driving said shaft to rotate said device.

18. The combination with a current-consuming device, means mounting saiddevice for rotation, a heavy-current generator adjacent said device forsup'plying current thereto, a slip-ring and brush assembly havingconductors extending to said device and generator, certain of saidconductors extending substantially axially from said assembly and otherssubstantially from the circumference thereof, and means mounting therelatively fixed portion of said assembly for rotation whereby to varythe position of the point at which said others extend therefrom.

19. The combination with a heavy-current load device and a slip-ring andbrush assembly connected thereto, of a heavy-current generator disposedadjacent aid assembly, and a plurality of th polarities extendingradially from said generator, the conductors of both polarities beinginterleaved between said generator and assembly.

20. The combination with a heavy-current load device and a slip-ring andbrush assembly connected thereto, of a heavy-current generator disposedadjacent said assembly, a plurality of conductors of both polaritiesextending radially from said generator, the conductors of bothpolarities being interleaved between said generator and assembly, andmeans mounting said assembly for adjusting movement relative to saidconductors.

21. The combination with a heavy-current load device and a slip-ring andbrush assembly connected thereto, of a heavy-current generator disposedadjacent said assembly, a plurality of conductors of both polaritiesextending radially from said generator, the conductors of bothpolarities being interleaved between said generator and assembly, andthe connections from the assembly to the device being arranged andconstructed so that the device may be adjusted relative to said 5

